Poor, Misunderstood Poison Ivy

Poor, Misunderstood Poison Ivy

[♪ INTRO] Nothing can ruin your vacation quite like an encounter with one of nature’s purveyors of itchiness. Of course, I’m talking about poison oak,
poison ivy, poison sumac, and their notorious relatives. Yes, these botanical nightmares are clearly out to make camping and hiking as miserable as possible. But maybe they’re not? Maybe they were just hanging out in the forest,
enjoying the fresh air, and trying to keep harmful microbes at bay, until you and your over-eager immune system
happened to come along. Poison ivy and the like are innocent. These plants all produce an oily resin called
urushiol. And it isn’t just in their leaves; it’s
in every part of them. And it remains even after the plant has died. This urushiol is what causes that notorious
itchy rash you get, or, what doctors call “urushiol-induced contact dermatitis.” Now, the leaves have to be crushed or somehow damaged in order for the urushiol to actually contact your skin, so you won’t get it by
just touching the plant. Of course, leaves and such are easily damaged
by insects, passing animals, or a stiff breeze, so just because you didn’t damage the leaves
yourself doesn’t mean something else didn’t get there first. In fact, because urushiol causes such a violent
rash in people, there’s this pervasive idea that the resin evolved as a defense mechanism
against large mammals like us. But that’s not true. Or at least, if it was a defense mechanism,
it would be a really lousy one, since urushiol doesn’t bother most animals that encounter it. Just us and apparently, hamsters. But it has no effect on the animals that actually
feed on the plant, like deer, insects, and birds. That’s why scientists think it’s more
likely that urushiol evolved as an antimicrobial, it’s quite effective against much smaller
plant pests. There’s even been some speculation that
birds that eat the seeds actually benefit from urushiol’s antimicrobial and anti-parasitic
properties. It’s simply an unfortunate accident of evolution
that makes these plants incompatible with humans. So, the rash, oozing blisters, and relentless
itching, it’s all pretty much down to cosmic unfairness. Urushiol interacts with your skin cells; specifically,
ones that express a protein called CD1a. CD1 proteins help the body spot invaders and
sick cells. They bind to specific fats, then show those
fats to the body’s immune cells. Except, human CD1a has the unfortunate tendency to set off attacks in response to things
that aren’t pathogenic. And it just so happens urushiol is one of
those things. Urushiol-loaded cells activate the body’s
T cells, those vigilant warriors of the human immune system. Then the T-cells release two proteins called
interleukin 17 and interleukin 22, and they’re what make you itch. The redness, swelling, and blisters all occur
because your immune system harms your skin cells in its attempts to eradicate a bit of
harmless oil. Now of course, this doesn’t really apply
to those 10-15% of humans who don’t seem to be affected by urushiol at all. For some reason, nature has seen fit to spare
some people from the horrors of urushiol, but there hasn’t been a lot of scientific
research into why that is. It might be because urushiol-induced contact
dermatitis is basically an allergy. And allergies occur when the body mistakes
a harmless substance for something harmful. And like with other allergies, some people’s immune systems just go haywire when encountering urushiol while others’ don’t. It’s just that most people are allergic
to urushiol. But also, some of the people who say they’re
immune probably aren’t really immune. Most people don’t react to urushiol the
first time they’re exposed, so a person might believe they’re immune when, in fact, they could go on to develop
an allergic reaction if they touch it again. And even if they’ve had a couple of exposures
with no reaction, they could still develop a sensitivity later in life. And increased exposure is thought to increase
the likelihood of developing sensitivity. So if they roll around in a bunch of poison
ivy to show off to their hyper-allergic friends, they might end up experiencing some itchy,
itchy karma. Though, weirdly enough, sometimes sensitivity
to urushiol fades as people get older. Scientists aren’t really sure why, but it
might have something to do with the fact that your immune system weakens as you get older. And a weaker immune system may not mount as
strong a defense against urushiol. So that’s one advantage to getting older! At any rate, whether you think you’re immune
or not, or may have become less sensitive over time, you probably don’t want to push
your luck. Urushiol-induced contact dermatitis is miserable
at any age. So it’s always a good idea to avoid whichever
version of poison-whatever is in your neighborhood. If you want to learn more about the quirks
of human immune systems, you might like our episode on how having parasites
could actually be good for you. And of course before you go, be sure to click
that subscribe button and ring the notification bell! Ding! Ding! Ding! Ding! Ding! Ding! Ding! [♪ OUTRO]


  • MountainMan says:

    Weird that this video popped up after i got poison ivy all over my body 🤔

  • Baby Bat Jack says:

    Actually, there are some people who have no reaction to them. My family is full of them and I'm one of those people. Poison sumac doesn't do anything but the others do in my case, in my mothers poison oak doesnt do anything but poison ivy and poison sumac do. Its weird.

  • Tiffany says:

    I'm one of those rare immune people. Parents found out the hard way when I was a little kid and was rolling all around in it at a lake and they freaked out and grabbed me to get me away from it. They ended up having the reaction but I was fine lol. Still aren't affected by it to this day.

  • Alec Risser says:

    I'm not allergic to any of these plants, ironically though, I do occasionally suffer from eczema. I wonder if there's a link between those two things? Perhaps what makes me predisposed to eczema is the same thing that makes me immune to these plants.

  • samotbrandon says:

    It seems like his mole keeps moving around his cheek.

  • santiago Ibarra says:

    Best short documentary research. I have always wanted to know about poison ivy and poison oak. Thanks.

  • fisqual says:

    I'm surprised there was no mention of raw cashews.

  • Joshua Kartchner says:

    I know a guy who wiped his butt with the stuff

  • Cuddlesmith5000 says:

    I'm one of the lucky ones. Used to maintain hiking trails and I was on the crew that always got to wade into the poison oak whenever we had to cut it back. Never did anything to me, but my cousin lend in for a hug one weekend and I didn't have the heart to insist he not do it… Yeah. I'm one of the lucky ones, not my cousin.

  • Tron_23 says:

    F poison ivy

  • N8c3z8nr N8x22z9yb4 says:

    Mango has urushiol in its skin

  • OldeOne deESuhrim says:

    I am not allergic to poison ivy, oak, or sumac. I am allergic to pineapple and milk thistle…. and most pharmaceuticals to which I have been exposed.

  • Losaiko Vote!!! says:

    If this stuff catches fire, run. You do.not want this stuff in your eyes or lungs. Some people do not seem to break out as bad and as you age you can get an immunity.

  • Douglas McNeil says:

    My father, back in the 1940's used to get paid by the local farmers the clear poison ivy from their fields and burn it. He never suffered any ill effects. I, myself have taken a hand full of leaves, crushed them in my hands and smeared them all over my face and arms on a dare. I've never suffered any ill effects. My mother on the other hand, was extremely allergic. To the point of needing hospitalization twice when she was young.

  • SAMURIADI says:

    we had to get nerfed somehow

  • Origami and Cats says:

    It's interesting because latex allergy works the same way. You become more likely to have the allergic reaction the more often you're exposed.

  • Jacob Bresler says:

    when I was growing up the hedges between my house and the neighbor were infested with poison Ivy, my brother and dad both got major reactions, I crawled through the hedges a few times and never had an issue which is interesting because I seem to be allergic to nearly everything else under the sun (I even got allergy shots when I was younger)

  • 01LincLS says:

    I never knew people could be so allergic to it until I was hospitalized for 3.5 weeks from it in July.

  • athena8794 says:

    I have no idea if I'm allergic to poison oak / ivy / sumac. I'm smart enough to stay the hell away from it, just in case.

    Though my granddad was immune, as long as he didn't have any breaks in the skin. Could wade through poison oak all day long (And sometimes did. He'd volunteer to clean out patches of it) provided he didn't have any cuts or scratches.

  • Kirk Morrison says:

    I can just go down wind of them and I break out. I have almost died from from reaction to poison ivy.

  • SayWhat? says:

    So if you can’t burn it safely then can you compost it to break the urushiol down?

  • dojokonojo says:

    A roommate brushed through poison oak during a hike and bathed in oatmeal, but left it all in the bathtub for a week. So, vegan hippie girl oatmeal bathwater…

  • Gareth Dean says:

    Poison ivy: Give it a hug.

  • Rollin With Uncle Pete says:

    My experiences with these miserable plants has not been pleasant! One time my mother had to take me to our family doctor for a cortisone shot because I was puffed-up like the Michelin Man!

  • TheGurumash says:

    I love Stefan, he's just the right amount of cheesy for Scishow.

  • Kiri Ximenez de Quesada says:

    I'm sad that I'm severely sensitive to this stuff

  • contrarian duude says:

    So Poison Ivy isn't just a hot spandex wearing super villain? Which begs the question why isn't there a super hot Poison Sumac?

  • Omor Shahid says:

    I love how this video is about leaves and it’s 4:20 long

  • t lech says:

    Grew up with poison oak in California first exposure was very bad every exposure after that within short durations of time became very small itchy spots while living in the area with poison oak to almost no results at all.
    After moving away to the city with no exposure for about three years then came back to a visit to my town I grew up in my first exposure to poison oak was horrible like the very first time I caught it and then exposure levels went down to almost nothing more than what looked like several flea bites after living there a year again been exposed. Some people build immunity

  • Mojos Bigstick says:

    Nettles sting intentionally, they don't get off the hook.

  • alemirdikson says:

    Just humans and hamsters?
    But dogs though.
    I've had to treat so many poison ivy rashes because my dogs wouldn't leave the stuff alone.
    You can't tell me they're immune too.

  • Saydjeny says:

    Never encountered poison ivy or its relatives myself. Apparently they only grow in North America.

  • Jessica Romo says:

    If you're allergic. Some people don't break out. Both my grandmother and mother have never had a reaction. I'm not brave enough to find out if I am immune. Considering I'm allergic to any thing that's green and grows, I doubt I'd have their immunity.

  • Donovan Beavers says:

    I used to have horrible reactions. I have brushed agaisnt poison oak a few time since and nothing. Still always worried, it itches and burns so bad.

  • Margot Robinson says:

    Urushiol is why cashews are never sold in the shell or sold raw. It’s also why you can’t eat the skin of a mango or raw pistachios.

  • MicManGuy says:

    Wait… poison ivy is just a dumb allergy?

  • Artificial Idiot says:

    I think having parasites mean i can eat loads of junk food and they'll suck that fat lol i think im very wrong

  • Selena Taylor says:

    The enthusiasm for the dings people! I loved them personally.

  • LagiNaLangAko23 says:

    Thank goodness we don't have these plants in my country. Then again, I don't leave my house.

  • ScoreUnderThis says:

    Urushiol sounds like a Harry Potter spell.

  • bob bill says:

    Just humans and hamsters huh? Lol

  • Greg Camp says:

    This makes me wonder if people with compromised immune systems suffer from allergies.

  • OtakuMage says:

    Don't forget that you don't need to touch the plants at all. Your dog or other animals can get the oil on them, not show any signs, and once you pet them….

  • Starfals says:

    As someone allergic to like 50 things, this is the 1 i always somehow get in contact with 😀 😀

  • joyful 09 says:

    You know what's not funny…

    People don't even actually know what causes cancer but I do… I just wish I could tell you…

  • SanctuaryReintegrate says:

    Ah, the spicy toilet paper.

  • anapolis says:

    lol aww poor hamsters

  • Random Guy In The Comments says:

    Aren't humans and hamsters, some of the only mammals that don't make their own vitamin C?

  • PeppermintPepperoni says:

    A video about a plant we don't like, that's got the time of a plant we DO like.

  • Riesenfriese says:

    "One benefit of getting older" Im not entirely convinced that becoming so weak that your body cant effectively hurt itself really qualifies as a benefit.

  • ImAd0pt3d says:

    So you’re telling me if I have aids my allergies won’t be as bad because my immune system will be trashed?

  • Charles haas says:

    I'm not allergic to any of those i think. Never got it and ally friends did while we walked the same paths

  • Hovzlozki says:

    Man I wish all that I had to worry about was some silly oil… Instead I have to look out for the Gympie Gympie plant…

  • PabloLovesP4 says:

    Are ppl with hiv- aids immune to poison ivy then?

  • weak sause says:

    I paused the video immediately after ads.
    I don't think I can watch this because I will break out. I am highly susceptible to poison oak and have gotten it through placebo in the past. If a rash appears exactly one week from today, I am going to kick myself in the nuts for watching this.

  • weak sause says:

    Scratching the bumps feels amazing good. That is the best early detection system. Normally when you scratch an itch, it relieves the itch. When you scratch poison oak rash, it feels sooo good.

    Once I discovered this, I became much less susceptible to the rash. I'll get a few bumps and scratch them. It feels amazing. Red flags go off in my brain: why did that scratch feel so good. Upon inspection I recognised the bumps for what they are and avoid contact for a few days.

  • EJ Tech and DIY says:

    Bob's burgers anyone?

  • AnteConfig says:

    I'm one of those special people who aren't effected by the poison of the ivy.
    Also if parasites are good for you then I think Americans should become familiar with tapeworms.

  • Suzette Henderson says:

    I used to not react, then BAM. Oh well.

  • Inkaword says:

    And I'm sitting here wondering what plant poison Ivy is in German before realising that it doesn't even grow in Europe

  • inue windwalker says:

    … but im not allergic to any of that, my big brothers and me used to sword fight with that crap lol

  • Always Random says:

    I grew up in the country. I've been around this stuff all my life. I'm pretty sure I've built a tolerance to this stuff. I never have a reaction to these plants anymore.

  • Jason Moore says:

    I'm one of the lucky people who are immune to Poison Ivy and the like. I found out when my brothers and I were playing in it. My brothers caught the rash and I didn't. Further proved this by picking the plant and wiping on my arms, Boom no rash.

  • overquoted says:

    I am highly allergic to poison ivy. I've had to get steroid shots because the reaction caused my hands to swell up. And I would suggest burning all poison ivy/oak, but that's how you ended up with an allergic reaction in your lungs. Screw these plants.

  • Blockman007 Guitarist says:

    Poison is french for fish

  • TheTimtam112 says:

    The fading over age may just be a limitation of the study done. If a participant hasn't been in contact with poison ivy for a long time, the memory t-cells that were created in order to mount a rapid response to urushiol may have simply died (not sure if this is why some vaccines require boosters or not). If we assume that older people are around poison ivy less because they have less time for exploring and that the researchers didn't do a longitudinal study where they test for a response on subjects they've previously exposed to urushiol.

    I'm spitballing here so take it with a grain of salt, just throwing some food for thought out there.

  • Jzwiz says:

    Im immune to poison ivy so im happy ill never have this issue (hopefully). Instead im allergic to ice cream :^) and anything with milk. Kinda wanna trade between the two.

  • Ed says:

    Oh…we are talking about the plant, i need to read less cartoons…

  • lombardo141 says:

    Am immune 🙋‍♂️…I cut them from my yard bare handed and nothing….👀

  • 1776 Style PATRIOT says:

    I know a guy that cuts trees for a living, every day when he is done he wipes his entire body down with his mixed chainsaw gas and he never ever had a reaction from poison ivy poison oak poison sumac or any poison at all!

  • Oliver Gs says:

    Could you please do a video on the Sydney funnelweb, which like these plants, coincidentally has venom which is only really dangerous to apes like humans. Even though it's a weird coincidence, it's extremely lethal and dangerous to us humans

  • 724warlord says:

    How come I don't get a rash from poison ivy?

  • B. Lonewolf says:

    Just imagine: What if someone got poison ivy on their PRIVATE areas? Ouch! :-O

  • Tylor Wendt says:

    You almost got the like taken away with the bell noise you made at the end.

  • TheLoneCabbage says:

    Not a defense mechanism…
    … it's an anti-microbial.

    So… it's a defense mechanism?

  • PoisonTheOgres says:

    I don't think we have anything like this in Europe? The only plant I was taught not to touch are stinging nettles and giant hogweed.

  • Fun Game says:

    So, what is the cure when you touch it?

  • Najee_eee says:

    Can you do an episode on how gimbals and gyroscopes work?

  • Arvin Medina says:

    hamsters left the chat

  • David G Austin says:

    I’ve never had a reaction to poison ivy, despite being with others who have gotten the rash. Are you telling me that my sense of well-being in the forest might be a lie?!?! I’m never going outside again…

  • Fanboy 3k says:

    I'm allergic to Poison Ivy last time I came in contact with it would have been in the 90s? And I had to go to the hospital because of the way it was ravaging my left arm. The swelling and weeping were crazy.

  • P. Gundaker says:

    My dad was sooo allergic and suffered badly from poison ivy. I would rub it all over myself and not have any effect. He hated me so badly lol

  • James m says:

    Would urushiol affect patients with HIV differently?

  • Khayre Tyler says:

    I've touched poison ivy and poison oak my entire life. My mom and her side of the family is the only one to have a reaction

  • Pierre Abbat says:

    No mention of Japanese lacquer? It's made from one of these plants, called "urushi" in Japanese.

  • Rizki Pratama says:

    Just us and hamster…. hmmm. Okay.

  • Sheila O'Neal says:

    Someone told me they were not allergic to it and then rubbed it all over their arm and then got the worst case of it I ever saw

  • This is a human Lol says:

    Nobody :
    Not a single soul :

    Stefan : ring a ding a ling!

  • Swinkscalibur says:

    People who are highly allergic to Urushiol should also be careful handling mangos

  • Limi V says:

    Me: lol lol lol lol

  • Rick Seiden says:

    I used to be immune to it, and I haven't tested it in a long time. But like Stephan said, things can change, and I'm not going to go looking for an opportunity to test if I'm still immune.

  • R2Walker says:


  • Don Blake says:

    Wow …interesting facts !! Thx

  • john pardon says:

    do we have em in europe as well? i only know nettles…

  • Mistah Bryan says:

    Don't care: I still want those plants destroyed.

  • zack walker says:

    👋 I’m one of those who’s not allergic to those itchy plants..

  • WRO says:

    Maybe if humans stop invading their natural ivy habitats, no one would get harmed.

  • Rick Harold says:

    Interesting! Thx

  • self discarded king of ruin 72 says:

    Who else here is unaffected by poison ivy?

  • FANGwoof says:

    Is this the same oil found on cashew nuts? I can't remember having a reaction to poison ivy but I developed a sensitivity to cashews a few years ago. Spoiler alert: it's very unpleasant.

Leave a Reply

Your email address will not be published. Required fields are marked *